By way of example, the envelopes of color cathode ray tubes (CRT's), of the shadow mask type often employed in television applications, are conventionally fabricated as an integration of neck, funnel and face panel components. The glass panel includes a viewing area having a cathodoluminescent screen interiorly formed thereon and a perimetrical sidewall therearound. The interior of the panel, including the screen and the surrounding panel sidewall, is usually metallized with a film of aluminum after formation of the patterned screen. This metallic film serves two functions: first, it provides a portion of the electrical conductive path for the screen potential, and second, it provides a reflective film upon the back of the screen thereby enhancing the frontal brightness thereof. Spatially positioned within the panel component is a multiple-opening mask component formed of a substantially domed foraminous portion, the edge of which is peripherally affixed to a rigid circumscribing framing member. This composite mask component, which is often referred to as a shadow mask, is supported within the panel, in spaced relationship to the viewing area and the surrounding sidewall, by a plurality of suitable positional means attached about the framing member in a manner to mate with supporting studs embedded in and projecting from the sidewall of the panel.
Upon completion of the screen fabricating procedure, the aforedescribed mask-panel assembly is hermetically sealed to the funnel component of the envelope. Electron generating means in the form of an integrated assembly comprising one or more electron guns, is then positioned and sealed within the neck component of the envelope, whereupon the tube is subsequently evacuated, sealed and processed.
In color CRT's of the shadow mask variety, the conventional operating screen potential is substantially that of the final anode electrode of the electron gun assembly, such being achieved by a diverse internal conductive path within the envelope. The final anode electrodes of the gun assembly usually make electrical contact through associated supportive snubber means with an electrically conductive coating, such as Aquadag, which is applied to the interior surface of the funnel component of the envelope. Usually, the highest operating potential is applied to this conductive coating by means of a button-type connection oriented through the wall of the funnel. The other differential potentials required for the successful operation of the electron guns in the assembly, are supplied to the respective electrodes therein by specific electrical conductive means terminating at the connective pins or leads traversing the closure portion and base of the tube. These protruding pins, in turn, are connected to suitable voltage sources external of the tube.
The final anode potential, which is supplied to the conductive coating on the interior surface of the funnel, is connected to the apertured mask by at least one resilient contact member attached to the mask framing member and extended therefrom to make pressured contact with the coating.
Exemplary electrical connection between the mask and screen components of the assembly is effected through the spaced-apart mask positioners in conjunction with the mating supporting studs protruding from the panel sidewall and the aluminized film disposed thereon. The studs are usually kept free of aluminum film to avoid the prevalence of metallic flakes resultant of subsequent mask positioning in the panel. Since the mask positioning means per se make riding contact on the wall-oriented supporting studs, electrical connection between the mask and the aluminized sidewall of the panel is provided by applying an area of an additional conductive coating, such as Aquadag, to a portion of at least one of the studs proper, making overlapping contact with the adjacent aluminum film to insure an electrical connection between the stud and the aluminum disposed on the panel sidewall. Since application of this discrete area of Aquadag is usually a manual operation, there have been occasions of inherent human deviation when the resultant electrical connection was less than desired. Additionally, deleterious effects have been evidenced in the form of erosion between the Aquadag and the aluminum film, accidental splashing of Aquadag on the screen, and the undesirable prevalence of scraped-off loose particles and flakes of Aquadag in the vicinity of the screen and mask.
Another means for achieving electrical connection between the mask and panel components of the mask-panel assembly is a resilient connective means of the type disclosed in U.S. Pat. No. 3,931,541, assigned to the assignee of this invention. The referred-to connective means, incorporated into the mask-panel assembly, is comprised of an attachment portion affixed to the framing member and an integral flexured contact portion located in a manner to extend forwardly in the spacing existent between the framing member and the conductive panel sidewall. There have been instances when careless insertion resulted in undesired abrasion of the aluminum film resulting in the possible presence of deleterious particlized material in the screen and mask regions.